linux-kernel - Re: [PATCH] smsdvb-debugfs.c: Fix error checking for debugfs_create

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Message-ID: <CAK6rUAO5PfprdShe3=6gnsUQ2rStpKxYvHcOek7A-CEJvaWO7A@mail.gmail.com>
Date:   Sun, 28 May 2023 20:12:52 +0500
From:   Osama Muhammad <osmtendev@...il.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] smsdvb-debugfs.c: Fix error checking for debugfs_create_file

Hi,

After researching more into it I have come to know that the debugfs
API will not return null on error but an ERR_PTR. The modern wisdom
about it is to ignore the errors returned by the function as stated in
the comment  above the function debugfs_create_file.

> * NOTE: it's expected that most callers should _ignore_ the errors returned
 >* by this function. Other debugfs functions handle the fact that the "dentry"
 >* passed to them could be an error and they don't crash in that case.
> * Drivers should generally work fine even if debugfs fails to init anyway.
Here is the link to comment :-
https://elixir.bootlin.com/linux/latest/source/fs/debugfs/inode.c#L451

Considering this, I will send the revision of the patch by removing
error checks. Please correct me if  there are any concerns with this.

Thanks,
Osmten



On Fri, 26 May 2023 at 15:53, Mauro Carvalho Chehab <mchehab@...nel.org> wrote:
>
> Em Wed, 24 May 2023 21:42:10 +0500
> Osama Muhammad <osmtendev@...il.com> escreveu:
>
> > This patch fixes the error checking in smsdvb-debugfs.c in
> > debugfs_create_file. The correct way to check if an error occurred
> > is using 'IS_ERR_OR_NULL' inline function.
> >
> > Signed-off-by: Osama Muhammad <osmtendev@...il.com>
> > ---
> >  drivers/media/common/siano/smsdvb-debugfs.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/common/siano/smsdvb-debugfs.c b/drivers/media/common/siano/smsdvb-debugfs.c
> > index 8916bb644756..0f8750d7993c 100644
> > --- a/drivers/media/common/siano/smsdvb-debugfs.c
> > +++ b/drivers/media/common/siano/smsdvb-debugfs.c
> > @@ -469,7 +469,7 @@ int smsdvb_debugfs_create(struct smsdvb_client_t *client)
> >
> >       d = debugfs_create_file("stats", S_IRUGO | S_IWUSR, client->debugfs,
> >                               client, &debugfs_stats_ops);
> > -     if (!d) {
> > +     if (IS_ERR_OR_NULL(d)) {
> >               debugfs_remove(client->debugfs);
> >               return -ENOMEM;
>
> if IS_ERR, it is probably better to return PTR_ERR(d).
>
> So, please change it accordingly, returning -ENOMEM only on NULL, e. g.
> something like (untested):
>
>         if (IS_ERR_OR_NULL(d)) {
>                 debugfs_remove(client->debugfs);
>                 if (!d)
>                         return -ENOMEM;
>                 return PTR_ERR(d);
>         }
>
> Regards,
> Mauro